Kate Mara goes from the car to the door of the Ed Sullivan Theater for the 'Late Show With David Letterman' on Feb. 18. / Ray Tamarra, WireImage

by Ann Oldenburg, USA TODAY

by Ann Oldenburg, USA TODAY

It has been tough to discuss House of Cards season two without spoiling major plot points for anyone who hasn't watched.

And that includes people involved in the show.

Kate Mara had to tiptoe around her character's storyline Tuesday night on the Late Show with David Letterman.

"Now I know something about season two of House of Cards and I never know whether I'm supposed to say things or not say things, so if you have something you want to say, you say it," Letterman said to the actress.

Pause.

"All I can say is I'm so happy to be alive and sitting here right now. I'm glad I took a car and not the subway to your show."

Bandleader Paul Shaffer interrupted with an "Uhhh," and pointed at Mara.

"But people know, right?" said Letterman, laughing.

"People that watched the first episode know, but, um, there's a lot of slowpokes out there," said Mara.

They discussed that some people have watched all the episodes that were released on Feb. 14. Others haven't watched any of it yet and Letterman doesn't want to ruin it for viewers.

"I don't want to be that one. I don't want to be that guy," said Letterman.